This invention relates in general to radar systems, and pertains particularly to a search radar effecting coordinated use of complementary antennae.
In some radar systems effective hemispherical searching coupled with rapid target acquisition that is highly immune to interference is desirable. For example, a search radar system used for tracking or fire-control must often detect and track small, threatening targets, including sea-skimming targets and fast moving targets. It must often react quickly to the detection of an in-range target in order to commence firing against it, while combatting interference such as multiple targets, jamming, heavy rain clutter, surface clutter, and chaff.
These requirements make it desirable to employ a narrow-beam antenna to combat the interference and provide accurate target positional data, in combination with a broad-beam antenna for rapid hemispherical searching. In addition, they encourage using dynamic response characteristics and associated mechanical parameters that have resisted implementation in the prior art.
Some multichannel and multiarray systems exist in the prior art that are slow and incapable of the separate antenna positioning ability required to implement full-function search radar systems of the quick reaction, antijamming type desired for tracking or fire-control. In U.S. Pat. No. 2,975,413, for example, a "Ground-Controlled Approach System" is described which employs separate elevation and azimuth antennae which are rotatable about a common search axis. The antennae must be stopped together, however, and the system does not lend itself to rapid target acquisition.
U.S. Pat. No. 3,007,151 describes separate elevation and azimuth antennae which are mounted on an antenna housing to rotate in mutually perpendicular planes for use alternately as a precision approach radar antenna or an air surveillance antenna.
U.S. Pat. No. 3,047,856 describes separate elevation and azimuth antennae driven by the same motor in a precision approach radar. The azimuth antenna rotates continuously and clutches are used to decrease its angular velocity as it scans past a landing approach path.
U.S. Pat. No. 3,113,310 describes a system employing two antenna arrays that can rotate together in azimuth while one of the arrays nods in elevation so that echo energy received by the arrays is cancelled when they are on target.
British Patent No. 455,765 describes two antenna arrays arranged to rotate about a common axis, with clutches for disconnecting the drive. However, rotation of one antenna about the common axis cannot be stopped while the other continues to rotate.
Japanese Patent No. 54-143047 describes a single radar channel using two antennae that are mounted on separate carriages to alternatively rotate about a common axis, wherein the carriages are interconnected so that stopping one of them causes the other to rotate.
These prior art systems do not meet the stringent requirements of a full-function tracking or fire-control radar system, and it is desirable to have a system employing both a broad-beam main antenna and a narrow-beam auxiliary antenna that can be coordinated to achieve the increased system functionality and efficiency required.